add exportProps to component as public infromation about component props interface

src/compiler/compile/render_dom/index.ts

@@ -440,9 +440,10 @@ export default function dom(
 				constructor(options) {
 					super();
 
+					this.exportProps = ${prop_names};
 					${css.code && b`this.shadowRoot.innerHTML = \`<style>${css.code.replace(/\\/g, '\\\\')}${options.dev ? `\n/*# sourceMappingURL=${css.map.toUrl()} */` : ''}</style>\`;`}
 
-					@init(this, { target: this.shadowRoot }, ${definition}, ${has_create_fragment ? 'create_fragment': 'null'}, ${not_equal}, ${prop_names});
+					@init(this, { target: this.shadowRoot }, ${definition}, ${has_create_fragment ? 'create_fragment': 'null'}, ${not_equal}, this.exportProps);
 
 					${dev_props_check}
 
@@ -493,8 +494,9 @@ export default function dom(
 			class ${name} extends ${superclass} {
 				constructor(options) {
 					super(${options.dev && `options`});
+					this.exportProps = ${prop_names};
 					${should_add_css && b`if (!@_document.getElementById("${component.stylesheet.id}-style")) ${add_css}();`}
-					@init(this, options, ${definition}, ${has_create_fragment ? 'create_fragment': 'null'}, ${not_equal}, ${prop_names});
+					@init(this, options, ${definition}, ${has_create_fragment ? 'create_fragment': 'null'}, ${not_equal}, this.exportProps);
 					${options.dev && b`@dispatch_dev("SvelteRegisterComponent", { component: this, tagName: "${name.name}", options, id: create_fragment.name });`}
 
 					${dev_props_check}